Exploring the intersection of brain injury and mental health in survivors of intimate partner violence: A scoping review

Rationale Intimate partner violence (IPV) is the most commonly occurring form of violence against women. The most common site of injury in IPV is the head, face, and neck, resulting in possible brain injury (BI). Independently, mental health (MH) concerns are highly prevalent among both IPV survivors and individuals with BI; however, no systematic review exists on the combined experience of BI and MH in IPV. Objective The aim of this review was to describe the identification of and relationships between BI, MH, and IPV in the literature and the implications for health policy and practice. Methods A search strategy including text words and subject headings related to BI, IPV, and MH was developed for MEDLINE and translated to EMBASE, PsycINFO, CINAHL, Cochrane, Scopus, and Web of Science. Two reviewers independently assessed articles for inclusion. Articles discussing MH, BI, and IPV in relation to one another were included in the review. Results Twenty-eight articles were identified for inclusion. Methods for identifying IPV, BI, and MH were highly variable across studies. Fourteen studies reported significantly higher MH scores in IPV survivors with BI than in those without BI. Articles predominantly focused on cis gender women in heterosexual relationships and the impact of race and ethnicity were largely overlooked. Healthcare access was explored by eight articles, though none discussed the implications of co-occurring BI and MH. Conclusion Brain injury and MH are highly prevalent among IPV survivors; however, little research discusses the implication for healthcare. Future research should explore healthcare-related needs and experiences to inform policy and practice and better represent the diversity of IPV survivors.


. Introduction
Recent estimates suggest 44% of women and 36% of men will experience intimate partner violence (IPV) in their lifetime, more than half of whom will experience physical violence (1). Intimate partner violence has been defined as physical, psychological, or sexual violence committed by an intimate partner or ex-partner and can result in significant emotional and bodily harm (2). Individuals of all genders and sexual orientations experience IPV; however, most research has focused on women survivors of IPV. Women experience higher rates and more severe forms of IPV than men, including higher rates of strangulation (1), and IPV is the most commonly experienced form of violence women experience (3,4). For the purposes of this review, we also include individuals working in sex work or prostitution under the umbrella of IPV. An estimated 45-81% of sex workers experience violence from their clients and many also experience violence from another intimate partner (5,6).
The COVID-19 pandemic has exacerbated IPV globally, significantly increasing both rates of IPV and the level of violence per encounter (7)(8)(9)(10)(11). Physical violence in IPV most commonly results in injury to the head, face, and neck (12), leaving survivors at high risk of traumatic brain injury (TBI). TBI is "an injury to the brain producing an alteration in brain function, or other evidence of brain pathology, caused by an external force" (13). Strangulation, also commonly experienced during IPV (1,14), can result in hypoxic-ischemic brain injury due to a lack of blood circulation and consequently oxygen and nutrients to the brain (15,16). Both hypoxic-ischemic and traumatic brain injuries have been included in this review under the umbrella of brain injury (BI), as the context of IPV similarly informs treatment and recovery challenges for both injuries (17)(18)(19).
Brain injuries from any cause can have significant longterm cognitive, psychiatric, physical, and social consequences (20)(21)(22)(23). Previous research indicates a high prevalence of BI among IPV survivors (14,24), suggesting a significant need for more attention to IPV-related BI. However, lack of awareness, gaps in screening, and unique challenges in healthcare access often leave BI overlooked in IPV survivors, hindering identification and support (14,17). Identification of IPV-related BI is further challenged by the high correlation between symptoms and sequelae of BI and symptoms of mental health (MH) concerns that are also commonly experienced by survivors (25-31). A recent Lancet Psychiatry Commission report focused on the intersection of IPV and MH noted the elevated risk of MH concerns among IPV survivors and the heightened risk of IPV among individuals, specifically women, with MH concerns (32). However, the report made no mention of head injury or BI of any kind, which is suggestive of the work still to be done in recognizing the triple intersection of IPV, MH concerns, and BI. The correlation between BI symptoms and MH concerns makes differential diagnosis difficult and further complicates the provision of and access to adequate and appropriate healthcare (25,33). The interaction between BI and MH concerns can impact care and treatment for the BI, MH concern, or both. For example, a BI can amplify the symptoms of post-traumatic stress disorder (PTSD), anxiety, or depression, making these MH concerns more difficult to treat if the underlying BI goes unaddressed (27,33). Furthermore, treatment for MH concerns may be more effective when accommodations are made for potential difficulties with emotion regulation, impulse control, pain, and cognitive limitations that can accompany BI (30).
Despite the high rates of both BI and MH concerns among survivors of IPV and the high rates of MH concerns among individuals with BI, the literature investigating the co-occurrence and combined experience of BI and MH concerns among survivors of IPV (triple intersection) is limited, and there has not yet, to our knowledge, been a comprehensive review investigating the intersection of BI and MH concerns among IPV survivors. An investigation into the triple intersection is needed as most of the research currently informing BI guidelines is based on predominantly male samples injured through other mechanisms (e.g., sports, military service).
This scoping review was developed to explore what is known in the literature about MH concerns and BI among survivors of IPV. Specifically, it aimed to summarize and synthesize the existing literature through the following objectives: (1) describe how IPV, BI, and MH concerns are identified in the literature and (2) describe the relationships between IPV, BI, and MH concerns. BI is often overlooked in IPV survivors with significant health implications, and MH concerns further complicate healthcare provision and access. Therefore, a third objective was to identify the implications for healthcare and health systems to inform policy and practice.

. Methods
This scoping review looked at MH concerns and BI among survivors of IPV as reported in the published literature since the inception of the searched databases. The review was designed following the framework first developed by Arksey and O'Malley (34) and further developed by JBI, formerly the Joanna Briggs Institute (35,36). Reporting was guided by the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) Checklist (37). The search strategy and eligibility criteria were informed by a previous scoping review investigating BI among survivors of IPV (14). Search terms for MH concerns were informed by a previous systematic review investigating MH and BI (38,39) and by the literature exploring MH implications of both BI and IPV (14,(25)(26)(27)(28)(40)(41)(42)(43).
. . Search strategy MEDLINE, EMBASE, PsycINFO, CINAHL, Cochrane, Scopus, and Web of Science were searched for relevant articles using a search strategy including text words and subject headings (e.g., MeSH, Emtree) related to BI, IPV, and MH. The search was initially run in October 2020 and revised and updated in January 2022 using concepts broadly characterized as follows: 1. Brain injury: Traumatic brain injury, concussion, head injury, post-concussion syndrome, strangulation, choking, face injury, and neck injury.
Sex workers are often excluded from IPV; however, there are many similarities in the violent encounters experienced by sex workers and IPV survivors. As such, previous reviews have chosen to include both IPV and sex work terms in their search (14), which we mirror in this review. For the complete search strategy, refer to Appendix A.
Searches were not limited by language, year of publication, or geographic location. Returned records were managed in EndNote and Covidence (44). A manual search of the reference lists of each article meeting the full-text inclusion criteria as well as any identified review articles discussing BI, MH concerns, and IPV was conducted to identify additional literature not captured in the original search.

. . Eligibility criteria: Title and abstract screen
Following the removal of duplicates, two reviewers (DT and either AM, SCG, or EC) independently assessed all identified titles and abstracts for eligibility. This screen focused on identifying primary research studies, including theses or dissertations, and review articles addressing BI among IPV survivors, MH concerns among IPV survivors, or IPV among individuals with BI. This broad approach was taken based on previous experience with reviews on BI suggesting that all relevant subgroups (in this case, IPV, MH, and BI) are not always included in the abstract, though relevant data may be presented in the body of the article. Articles were excluded if they focused on the perpetrator, on populations younger than 18 years of age, or on violence outside of the context of an intimate partner relationship. Conference abstracts, protocols, books or book reviews, and animal studies were also excluded. Covidence software was used for screening and to monitor agreement between the reviewers' assessments (87-94% agreement between pairs). Differences were resolved through discussion and consensus; articles were moved to the full-text screen if consensus could not be reached.

. . Eligibility criteria: Full-text screen
Full texts were again reviewed independently by two reviewers (DT and either AM, SCG, or EC). For inclusion in the review, studies needed to specifically discuss MH concerns and BI in survivors of IPV, be written in English, and be available through the University of Toronto Library system. Exclusion criteria used for the abstract and title screen continued to apply. In addition, articles were excluded if they were commentaries or if they did not discuss MH, BI, and IPV in relation to one another (e.g., discussing MH and BI separately). As with the title and abstract screen, Covidence software was used to conduct the screening and monitor agreement between the reviewers' assessments (80-96% agreement between pairs). All differences in screening were resolved through discussion and consensus.

. . Data extraction and synthesis
Study details (i.e., location, design, population, sample size, data source, definitions for IPV, BI, and MH) and key findings (prevalence of IPV, BI, and MH; healthcare use; relationships between IPV, BI, and MH) were extracted from included studies as reported. Data were extracted by one reviewer and peer-reviewed by a second (DT and AM or EC) then synthesized using narrative synthesis (45).

. Results
Searching the seven databases returned 753 results and 563 unique records following duplicate removal. From this body of literature, a total of 28 articles reporting on 27 studies (including three theses) were included. For a comprehensive breakdown of the article review process, please refer to Figure 1.

. . Article characteristics and study populations
Articles were predominantly published in the last 5 years (61%, n = 17) and based on data from the United States (US; 82%, n = 23). Study populations consisted almost exclusively of women or female survivors, with a few noted exceptions. Three studies included male survivors in their sample, accounting for 3-10% of the study populations (47-49). Gabbe et al. (50) found 27% of major trauma patients presenting with TBI caused by IPV-related violence were male. While both male and female survivors were included in these studies, sex-or gender-specific findings were not reported, though small sample sizes were likely prohibitive of that reporting. Four studies specifically reported on the sex or gender of the perpetrator, all specifying males or men as perpetrators (51)(52)(53)(54). One additional study noted the study population as heterosexual women (55).
Two studies specifically explored the experiences of Black or African American women (56, 57), and one study focused on the experiences of Chinese women (58). The remainder of the studies had variable reporting on race or ethnicity. Four articles reported on the percentage of participants that were non-white (ranging from 4 to 62% stratified by BI status) (27,59,60) or from a visible minority (13%) (61). Five articles reported on the number of participants who were Black/African American or white with the remainder in a mixed race or other categories (40,52,55,62,63). Nine articles reported on all groups represented in the sample (10, 43,47,49,51,54,[64][65][66], and seven articles did not report race or ethnicity at all (48,50,53,(67)(68)(69)(70). Among studies where race or ethnicity was not an inclusion criterion, white (n = 14 studies, 8-75%), African American/Black (n = 13, 13-90%),  and Latina/Hispanic (n = 6, 1-16%) were the most commonly reported groups. Some studies controlled for sociodemographic factors (including race or ethnicity) in their analyses; however, none reported race-or ethnicity-specific findings. Though the search terms were broadened to include sex work, none of the included studies focused on or included individuals who participate in sex work or prostitution. However, the inclusion of strangulation in our search terms was mirrored to a large extent in the literature. Although most articles referred to TBI, 15 of the 28 included articles (54%) included strangulation in their definition of TBI. In addition, five articles focused specifically on strangulation (51,54,55,66,69). One of these articles, reporting on findings from a broader study investigating BI (43), specifically looked at strangulation-related alterations in consciousness (66); however, three of the remaining four articles reported high rates of loss of consciousness or dizziness among their study participants, indicative of a potential BI (51,54,69
While most studies included individuals who had experienced IPV at any point in their lifetime, there were several studies that required IPV within a certain timeframe. Four studies assessed for IPV within the last year (27, 51, 58,

. . . Assessing for brain injury (BI)
Identification of BI varied greatly across studies. In most instances, studies assessed for possible or probable BI by asking about instances of hits to the head, face, or neck followed by a period of altered or loss of consciousness, or by asking about instances of strangulation or choking. More than half of the included studies (n = 15) assessed for BI using screening tools or diagnostic interviews, with the Boston Assessment of TBI (62,63,67), Brain Injury Severity Assessment (61, 66,68), and Veterans Affairs TBI screening tool (27,59,60) the most commonly used in three studies each. Gabbe                  Articles reporting on the same study. * Indicates a note or comment related to inclusion/exclusion criteria.
via EEG. Three of the five studies focusing on strangulation simply asked if or how frequently survivors had been choked and/or strangled (51,54,55). The remainder of the studies assessed for BI using self-report that was not further specified. Some studies specifically excluded individuals with more severe BI (58,66) or BI that was not IPV related (43,49,57,66) and a subset of studies reported on BI from other causes in addition to IPV-BI (61, 62, 64, 66, 67). As previously noted, most articles discussed BI broadly, including both TBI and strangulation (n = 15). Some focused on TBI specifically (n = 8), and others focused on strangulation (n = 5). Table 1 shows included articles stratified by these categories. Several studies in each category had BI as an inclusion criterion (40,48,50,51,53,59,69). Among studies where BI was not an inclusion criterion, the prevalence of strangulation ranged from 13 (56) to 93% (49), the prevalence of BI ranged from 19 (60) to 100% (68), and the prevalence of TBI ranged from 21 (64) to 69% (47). There was also a noted relationship between BI and IPV scores or experiences. Mittal et al. (55) reported significantly higher scores on two IPV scales among women who were strangled compared to women who were not, and Wong et al. (58) reported a significant association between past-year psychological (but not physical or sexual) abuse and IPV-related mild TBI.

. . Experiences of BI and MH concerns in survivors of IPV
All studies in this review specifically discussed MH, BI, and IPV in relation to one another, allowing us to explore the intersectional impact of MH concerns and BI among IPV survivors. All but three of the 28 included articles reported on MH concerns among survivors of IPV with BI. Those three looked at rates of IPV among individuals with BI, reporting on MH prevalence within that subset (50); and rates of BI among survivors of IPV with positive screen and diagnosis of PTSD, respectively (62,63).
Relationships between BI and MH concerns among IPV survivors were also explored in 14 studies. Studies reported statistically significant differences in PTSD scores (27,56,57,60,(64)(65)(66)(67), depression scores (55,60,66), anxiety scores (57), or composite mental health scores (56, 58) among IPV survivors with BI compared to those without. Two studies compared MH scores with BI severity scores rather than grouping survivors with and without BI, both reporting significant positive associations between BI and MH scores (43,47). Furthermore, the presence of BI was noted to negatively impact outcomes in PTSD treatment (63), and persistent BI symptoms were associated with lingering insomnia, depression, and physical health concerns (59). McFadgion (65) also reported that IPV survivors who experienced post-traumatic stress symptoms were more likely to experience a blow to the head from physical abuse. Two qualitative studies exploring experiences of BI among survivors of IPV noted MH concerns were often exacerbated following physical abuse (51) and negatively impacted by the COVID-19 pandemic (10). It was further noted that survivors often continued to experience MH concerns even after leaving the abusive relationship (51).

. . Healthcare use and access
Many studies identified implications for health and healthcare among IPV survivors with BI and MH; however, less than half investigated healthcare use or access. Seven studies used healthcare settings for some or all their participant recruitment (50, 54-56, 58, 60, 69), two of which also reported healthcare seeking (54,69). An additional five studies reported the number of survivors who sought healthcare because of IPV (40,51,52,64,70). One article specifically compared health service use among IPV survivors with and without BI, reporting significantly higher Veterans Affairs healthcare use among women veteran IPV survivors with BI than those without (60). Studies reported 18-62% of survivors received care for an IPV-related injury at some point following the abuse (40,51,52,54,64,69,70). A qualitative exploration of care seeking identified fear of the abuser and a reluctance to discuss the experience of IPV as barriers (51).

. Discussion
This review identified 28 trail-blazing articles discussing BI and MH concerns among survivors of IPV. Studies focused on cis gender women in relationships with men and were predominantly conducted in the US. Overall, the prevalence of BI (strangulation, TBI, or both) among IPV survivors ranged from 13 to 93%, which is in line with previous estimations (14). The prevalence of MH concerns among IPV-BI survivors, which has not previously been assessed in a review, ranged from 25 to 100%. Studies used a wide range of methods for identifying IPV, MH, and BI, including via recruitment settings, single self-report questions, validated questionnaires, and medical diagnoses. These differences are likely to contribute to the large ranges in prevalence seen across studies.
Many studies reported significant differences in MH scores between IPV survivors with BI compared to those without or significant correlations between BI and MH scores. Though only explored in two studies, BI was shown to negatively impact PTSD treatment outcomes and both physical and mental health. The prevalence of healthcare seeking was explored in a subset of studies, ranging from 18 to 62% among studies that did not recruit solely from healthcare sites. One of those studies reported higher care use among IPV survivors with BI than those without (60). Fear of the abuser and a reluctance to discuss the experience were noted as barriers to accessing care (51).
This review highlights the small but growing pool of foundational work on the intersection of MH concerns and BI among IPV survivors, underscoring the high prevalence of cooccurring MH and BI among IPV survivors and identifying opportunities for future exploration, including the investigation into the healthcare-related impacts of this intersection on survivors and the health system. The high rate of BI among survivors combined with the higher severity of MH associated with BI indicates this is a significant intersection for investigation not only for healthcare systems but also for community care systems and society at large. As much is still unknown about this intersection, four broad categories in need of further investigation are highlighted below.

. . Identification
Defining and screening for BI among IPV survivors is an ongoing debate in the IPV-BI literature (14,48,72). While loss of consciousness is a strong indicator of BI, more subtle alterations of consciousness (e.g., feeling dazed, confused, seeing stars) are also indicative of BI (56) but may not be captured depending on the way questions are worded and the survivor's memory of the incident. Given that almost all the included studies relied on survivor selfreport, and the measures used varied from asking about specific injuries resulting in loss of consciousness to any injury resulting in the alteration of consciousness, it is likely that even when using BI screening measures, BIs are missed among IPV survivors. Several studies reported on BI both as identified via screening tools and as identified through questions about hits to the head with alterations in or loss of consciousness. In some cases, the prevalence using the latter method was double that of the former.
It is worth noting that the identification of IPV, particularly in healthcare settings, poses its own challenges. In addition to the challenges with IPV survivors not wanting or being able to seek treatment noted in the included literature, there are also challenges with the identification and disclosure of IPV when survivors do seek care. Medical professionals may be reluctant to broach the topic for reasons including lack of training or resources to do so or a belief that IPV is beyond their scope of practice. This, combined with a survivor's reluctance to disclose, can impede

. . Sex and gender
The studies included in this review focused predominantly on cis gender women in relationships with men. However, there were inconsistencies throughout the included studies in referring to survivors as women, which aligns with the social construct of gender, and as females, which aligns with physiological sex. Similar inconsistencies were found in the reporting of partner sex and/or gender. As the experience of BI is influenced by both sex and gender (73)(74)(75), and IPV impacts individuals across the gender spectrum, there is an opportunity in this growing field to explore experiences of BI and MH concerns across IPV survivors of all genders and sexes.

. . Healthcare seeking
Included articles that explored healthcare predominantly focused on whether or not women sought medical help, rather than survivors' self-perceived health needs or how comorbid conditions shaped their care-seeking. The experience of care seeking, whether through medical or community routes, and perceived care needs is an opportunity for exploration. Several articles provided recommendations for healthcare providers in their discussions; the field would benefit from an investigation of how survivors experienced healthcare or other services that could further develop those recommendations. This call is echoed in the literature, identifying the triple intersection as needing more focus particularly because MH that is comorbid with BI, both in IPV survivors and the broader population, requires different considerations for care and treatment than MH alone, and vice versa (31,(76)(77)(78).
An additional consideration in the discussion of care-seeking is the healthcare and social context in which the study was conducted. Only five of the included articles were conducted outside of the US (10, 50,58,61,68). While there are many aspects of the lived experience of BI, IPV, and MH that are universal, context also plays a role. Financial accessibility of healthcare has implications for care-seeking. More research in diverse contexts with different healthcare systems, including systems with universal healthcare, would support a more complete understanding of survivor needs and experiences. The one study reporting on healthcare use among IPV survivors with BI found increased Veterans Affairs healthcare use, which is funded for US veterans (60). Further investigation of the experiences of IPV-related BI and MH in contexts outside of the US will be critical for shaping the response to this "parallel pandemic" of COVID-19 and IPV, particularly when it comes to healthcare or service access and use. For example, in April 2020, the Government of Canada acknowledged IPV as a critical problem, exacerbated by COVID-19, and invested $207.5 million to support organizations addressing homelessness and women experiencing gender-based violence (79). Given the system-wide barriers and challenges identified with respect to the IPV-BI intersection overall (80), more research in this area could help target future investments to the areas with the greatest impact.

. . Intersectional representation
Throughout the literature included in this study, the intersection of other aspects of identity, such as race, ethnicity, ability, or immigration status, and the impacts of MH and BI among IPV survivors remains largely unexplored. Three studies focused on the experiences of specific ethnic groups (56-58) and one case report discussed the experiences of two refugees identifying as IPV survivors with BI (53); however, only one of the cases explored the triple intersection. A more thorough look into the impact of intersecting identities is needed as there are increased risks and differing care needs for these groups. For example, Indigenous women are at particularly high risk for IPV, reporting 2.5 times higher rates of violence and a higher rate of resultant injury (81), yet preliminary work in the IPV-BI intersection working with Indigenous groups in Canada (82) suggests that resources developed for urban settler populations are ineffective for many First Nations and Inuit communities for myriad reasons. A collaborative, Indigenous-led approach to developing culturally sensitive community-based resources and interventions is needed to support Indigenous survivors and their communities.

. . Strengths and limitations
This scoping review is the first, to the best of our knowledge, exploring the combined experience of IPV, BI, and MH. It provides insight into the prevalence of BI and MH among IPV survivors; identifies the wide variety of methods used to identify BI, MH, and IPV; and synthesizes the relationships between them as currently understood in the literature. The review used a comprehensive and purposefully broad search strategy across five databases that were not limited by date or language, maximizing the published literature captured in the initial search. The twostage, systematic screening process, as well as the high proportion of agreement among reviewers, further minimized the risk of excluding relevant articles.
We acknowledge several limitations to this review. While the search was not limited by language, we were not able to review full-text articles in languages other than English, resulting in the exclusion of five articles at the full-text stage (3% of articles reviewed). In addition, any unpublished literature, reports, or briefs that may be present in gray literature were not captured in our search. Including gray literature has the noted benefit of providing a more comprehensive overview of available evidence on a subject; but, its inclusion poses a significant challenge in the increased human resources required to find, manage, and review these records (83). Unfortunately, due to resource limitations, a systematic search of the gray literature was not possible. Finally, we recognize that the findings presented are limited by the included literature, which predominantly used small (N < 50) convenience samples. It can be challenging to engage IPV survivors in research for a variety of reasons including willingness to disclose and safety concerns. Furthermore, many of the studies recruited through shelters and related domestic violence support centers, which impacts the type of individuals captured in the research.

. . Latest contributions
The literature focusing on the triple intersection is growing rapidly, as indicated by the majority of the included articles being published in the last 5 years. In the time between running our last database search and the publication of this review, we are aware of the publication of three additional articles reporting on the triple intersection. Chiou et al. (84) investigated depression severity in a subsample of IPV-BI survivors explored in another article included in this review (70), finding 64% of their participants endorsing moderate to severe depression based on the Beck Depression Inventory. Oakley et al. (85) assessed the willingness of IPV survivors to be screened for BI, with 88% of their sample screening positive for probable TBI on the HELPS tool. Among the sample with a positive TBI screen, 89 and 78% reported depression and anxiety, respectively. Finally, Quiroz Molinares et al. (86) explored BI among Colombian women survivors of IPV, finding 31% experienced BI and a significant correlation between BI score and depression when controlling for abuse severity and various socioeconomic factors. The findings from these articles align with those reported in the review.

. Conclusion
This review highlighted the foundational and growing pool of literature on the triple intersection of IPV, BI, and MH and draws attention to the numerous opportunities for future work, such as increasing our understanding of BI and MH among IPV survivors, better representing the diversity of individuals experiencing IPV, and exploring service-related needs and experiences to inform policy and practice.

Data availability statement
All data analyzed as part of this scoping review is from publicly available published literature.

Author contributions
This study was conceptualized by DT, HLH, AC, and CMW in consultation with EN and VC. DT developed the search strategy, ran the database searches finalized analyses, and drafted the manuscript. DT, AM, EC, and SCG conducted screening and contributed to the analyses. All authors contributed to the manuscript revision, read, and approved the submitted version.

Funding
DT and HLH were supported by a grant from the Ontario Neurotrauma Foundation and the Ontario Women's Health Scholar Award. This research was undertaken, in part, thanks to funding from the Canada Research Chairs Program.